1. Field of the Invention
This invention relates to an electrical connecting member for use when electric circuit parts are electrically connected together and a method of manufacturing the same.
2. Related Background Art
The wire bonding method and the TAB (tape automated bonding) method are known as a method of electrically connecting the electric circuit parts of a printed substrate, an integrated circuit or the like together. However, these methods have both been costly and moreover have suffered from the difficulty that the number of connection points between electric circuit parts is increased and the increase cannot be coped with if the connection point density becomes high.
There is known a technique of electrically connecting electric circuit parts together by the use of an electrical connecting member having a plurality of electrically conductive members provided in a mutually insulated state in an insulative holding member to overcome the above-noted difficulty.
As such an electrical connecting member, there is one proposed in Japanese Laid-Open Patent Application No. 2-49385. This technique will hereinafter be described with reference to FIGS. 1 and 2 of the accompanying drawings.
FIG. 1 is a plan view of an electrical connecting member 41 according to the prior art, and FIG. 2 is a longitudinal cross-sectional view thereof. This electrical connecting member 41 is comprised of a film-like holding member 42 formed of an electrically insulative material and a plurality of electrically conductive members 45 provided in a mutually insulated state in apertures 43 formed at predetermined intervals in the holding member 42. One end of each of the electrically conductive members 45 is exposed in such a manner as to slightly protrude on one surface of the holding member 42, and the other end thereof is exposed in such a manner as to slightly protrude on the other surface of the holding member 42, and the diameter of these exposed end portions is slightly larger than the diameter of the apertures 43, and the exposed end portions are stopped from slipping out of the apertures 43.
As regards the dimensions of the various portions of the electrical connecting member 41, as shown in FIG. 4 of the accompanying drawings, the thickness of the holding member 42 is about 10 .mu.m, the diameter of each aperture 43 (the post-like portion of the electrically conductive member) is about 20 .mu.m, the pitch between the apertures 43 is about 40 .mu.m, and the height of protrusion of each electrically conductive member 45 on each of the front and back surfaces of the holding member is of the order of several .mu.m. Such an electrical connecting member is manufactured by a process as shown in FIGS. 3A to 3E of the accompanying drawings.
FIGS. 3A to 3E are schematic cross-sectional views showing the essential steps of a method of manufacturing the electrical connecting member according to the prior art. A metal sheet 51 which provides a base body is first prepared (FIG. 3A), and negative-type photosensitive resin 52 constituting the holding member 42 is applied onto the metal sheet 51 by a spinner and is pre-baked (FIG. 3B). Light is applied to the photosensitive resin 52 through a photomask (not shown) which forms a predetermined pattern to thereby expose the photosensitive resin 52 to the light, and development is effected (FIG. 3C). Thereby, the photosensitive resin 52 remains on the exposed portion, and in the unexposed portion, the photosensitive resin 52 is removed by the developing process, and apertures 53 in which the surface of the metal sheet is exposed on the bottom are formed. Temperature is increased to thereby effect the curing of the photosensitive resin 52, whereafter these are immersed in etching liquid to thereby expose each the surface of the metal sheet 51 in the apertures 53, and recesses 54 are formed there (FIG. 3D).
The apertures 53 and the recesses 54 are then filled with gold 55 constituting the electrically conductive members 54, and the electrically conductive members 45 are gold-plated so as to be protuberant to a predetermined height from the surface of the photosensitive resin 52, thereby forming bumps (FIG. 3E). Finally, the metal sheet 51 is removed by etching, whereby the electrical connecting member 41 in which the gold 55 and the photosensitive resin 52 constitute the electrically conductive members 45 and the holding member 42, respectively, as shown in FIG. 2, is manufactured.
FIG. 4A of the accompanying drawings is a schematic view showing electric circuit parts 61, 62 and the electrical connecting member 41 before they are connected together, and FIG. 4B of the accompanying drawings is a schematic view showing the electric circuit parts 61, 62 and the electrical connecting member 41 after they are connected together. The electric circuit parts 61 and 62 are those of a printed substrate or the like which are to be connected together. One electric circuit part 61 is opposed to that side of the electrical connecting member 41 on which one end 45a of each electrically conductive member 45 is exposed, and the other electric circuit part 62 is opposed to that side of the electrical connecting member 41 on which the other end 45b of each electrically conductive member 45 is exposed (FIG. 4A). The connecting portions 66 and 67 of the electric circuit parts 61 and 62, respectively, and the ends 45a and 45b of the electrically conductive members 45 are brought into pressure contact with each other while being heated and are made into an alloy, whereby they are connected together.
Now, when the electrical connecting member 41 as described above is used for the connection of the electric circuit parts, the holding member 42 of polyimide resin or the like still remains around the electrically conductive members 45 after the connection. Accordingly, there is the problem that if a temperature change occurs after the connection and the holding member 42 is thermally expanded, strong stress will be imparted to the electrically conductive members 45 by the expanded holding member 42, whereby the electrically conductive members 45 may be damaged or severed.
Further, in the electrical connecting member 41 as described above, the concentration of stress may be caused in the electrically conductive members 45 and the joint portions of these to electrodes 40, 50 by the actions of the forces in directions other than the direction of pressure contact during the pressure contact of the electrodes 40, 50 and the action of the thermal stress after the connection, and in such case, there is the problem that cracks occur in the electrically conductive members 45, the joint portions and the holding member 42 and when the concentration of heavy stress occurs, the electrically conductive members 45 or the holding member 42 may be fractured to cause an increase in electrical resistance and unsatisfactory conduction.